The present invention relates to a guide wire, particularly to a guide wire for use in introducing a catheter into a body lumen such as a blood vessel.
Guide wires are used to guide a catheter in treatment of cites at which open surgeries are difficult or which require low invasiveness to the body, for example, PTCA (Percutaneous Transluminal Coronary Angioplasty), or in diagnosis such as cardioangiography, and for the like purposes.
A guide wire used in the PTCA procedure is inserted, with its distal end projecting from the distal end of a balloon catheter, into the vicinity of a target angiostenosis portion together with the balloon catheter, and is thus used to guide the distal end portion of the balloon catheter to the vicinity of the target angiostenosis portion.
Particularly, a guide wire used to insert a balloon catheter into a blood vessel is required to go forward in a complicatedly meandering blood vessel, and is therefore required to have sufficient flexibility and restoring performance against bending, pushability and torque transmission performance (these are altogether called operationality) for securely transmitting an operational force from the proximal end portion to the distal end side, kink resistance, and the like.
In the conventional guide wires, the core member is substantially made of a single material. Therefore, the flexibility of the distal end portion of the guide wire is lost where a material having a comparatively high elastic modulus is used for forming the core member in order to enhance the operationality of the guide wire. On the other hand, if a material having a comparatively low elastic modulus is used for the core member in order to obtain flexibility at the distal end portion of the guide wire, the operationality on the proximal end side of the guide wire is lost. Thus, it has been regarded as difficult to satisfy both the requirements of flexibility and operationality by using a core member made of a single material.
U.S. Pat. No. 5,171,383 proposes a guide wire in which an Ni-Ti alloy wire is used as a core member, and the distal end side and the proximal end side of the alloy wire are heat-treated under different conditions in order to enhance flexibility of a distal end portion of the guide wire and to enhance rigidity on the proximal end side of the guide wire.
In addition, U.S. Pat. No. 6,001,068 proposes a guide wire which is comprised of a flexible wire disposed on the distal end side, a high rigidity wire disposed on the proximal end side, and a tubular joint member having a groove and a slit for connection between the first wire and the second wire, wherein the joint member is gradually raised in rigidity from the distal end side toward the proximal end side thereof.